[sdiy] Filter slopes

[Ian Fritz]

Doesn’t Dieter do that with his delay units?  

Ian

> On Jun 11, 2018, at 5:17 PM, Scott Gravenhorst <music.maker at gte.net> wrote:
> 
> 
> Also, a friend of mine, Les Hall on electro-music.com, came up with an analog way to do
> Karplus-Strong using a BBD and a single pole low pass analog filter (just RC) in the loop. 
> This works and might also be applicable to the flute model described on ccrma.standford.com. 
> That might be tricky to get working, but probably not impossible.  If I were to try it (I'm not
> really an analog guy now), I'd start with Les Hall's BBD KS circuit and see what the problems
> are with it.  Another friend implemented it (BBD KS) and he said it suffers the same problem
> that the digital model has - the low pass filter adds a bit of extra delay so it detunes a bit
> as the delay is shortened.  Delay time is controlled by using a VCO as a clock to drive the BBD.
> 
> music.maker at gte.net wrote:
>> 
>> 
>> Look at Perry Cook's flute model:
>> 
>> https://ccrma.stanford.edu/software/clm/compmus/clm-tutorials/pm.html#s-f
>> 
>> It's an extension of Karplus-Strong string models. There are two 
>> delay lines, one is exactly 1/2 the length of the other. The 
>> short one models the mouthpiece and it energizes the long one. 
>> I've gotten it to work and it sounds VERY flute-like, however, I 
>> still need to work on it because it comes to full amplitude very 
>> slowly with whatever mistake I made. I'm sure another look at my 
>> code and I'll see a doofus thing I did. 
>> 
>> Tom Wiltshire <tom at electricdruid.net> wrote:
>>> Ok, I don’t know anything about “coupled resonators”. What 
>>> would I look up to find out more (aside from that obvious term ), 
>>> and how would I implement such a thing for analogue audio? Making 
>>> “resonators” is easy enough. How do I “couple” them? 
>>> 
>>> I’m looking for a practical implementation with details of how 
>>> that was arrived at, rather than a highly abstract splurge of 
>>> math that I won't understand and which could probably be 
>>> explained in words of two syllables or less if anyone took the 
>>> time to bother. 
>>> 
>>> Thanks,
>>> Tom
>>> 
>>> ==================
>>>      Electric Druid
>>> Synth & Stompbox DIY
>>> ==================
>>> 
>>>> On 11 Jun 2018, at 20:50, ASSI <Stromeko at nexgo.de> wrote:
>>>> 
>>>> On Monday, June 11, 2018 7:43:22 AM CEST Elain Klopke wrote:
>>>>> I was reading an article about the spectral content of various instruments
>>>>> (woodwinds and strings) and while they didn't have any circuits, there were
>>>>> some tables showing cutoff frequencies and high and low slopes. Several of
>>>>> the pictures looked like bandpass filter responses with different slopes on
>>>>> each side. How would I go about doing that? Is the slope determined by the
>>>>> gain of the op amp in an active filter? If it's that easy, would it be a
>>>>> highpass filter followed by a lowpass filter each with their own gain
>>>>> settings?
>>>> 
>>>> Both woodwinds and string instruments (among others) can be modeled with 
>>>> coupled resonators.  The characteristic timbre of each is related to the modes 
>>>> of these resonators and the transfer of energy between them.  The slopes of 
>>>> the bandpass skirts depend on both the quality factor of the resonator and the 
>>>> coupling strength to other resonators or resonator modes.  Generally speaking, 
>>>> losing energy (e.g. into another mode) is a reduction in Q and hence shows up 
>>>> as a flattening of the slope.  If you just want to approximate the magnitude 
>>>> response, a filter bank with a high enough number of filter bands is as good 
>>>> as any other method and relatively easy to implement, it just uses many de-
>>>> coupled resonators instead of few(er) coupled ones.
>>>> 
>>>> 
>>>> Regards,
>>>> Achim.
>>>> -- 
>>>> +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
>>>> 
>>>> Wavetables for the Terratec KOMPLEXER:
>>>> http://Synth.Stromeko.net/Downloads.html#KomplexerWaves
>>>> 
>>>> 
>>>> 
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>> 
>> -- ScottG
>> ________________________________________________________________________
>> -- Scott Gravenhorst
>> -- http://scott.joviansynth.com/
>> -- When the going gets tough, the tough use the command line.
>> -- Matt 21:22
>> 
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> 
> -- ScottG
> ________________________________________________________________________
> -- Scott Gravenhorst
> -- http://scott.joviansynth.com/
> -- When the going gets tough, the tough use the command line.
> -- Matt 21:22
> 
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